Cathode ray oscillograph tube



Nov. 13, 1934. BEDFORD r AL 1,980,177

CATHODE RAY OSCILLOGRAPH TUBE Filed Feb. 6, 1932 c. a. COL/ENE) I (Media ATTORNEY Patented Nov. 13, 1934 UNITED STATES PATENT OFFICE CATHODE RAY OSCILLOGRAPH TUBE Application February 6, 1932, Serial No. 591,393 In Great Britain March 16, 1931 6 Claims.

This invention relates to cathode ray oscillograph tubes, and has for its object the production of a tube having improved characteristics, a longer useful life and high sensitivity.

According to the present invention, a cathode ray oscillograph tube comprises a disc anode with an aperture therein for focussing the cathode rays, the anode being carried by the rods supporting the deflector plates.

Another feature of the invention is the use of a shield around the emissive cathode for the purpose of assisting the focussing of the rays.

A further feature of the invention is the use of an emissive cathode of very small virtual area.

These and other features of the invention will be more readily understood from the following description in which reference will be made to the accompanying drawing, Fig. 1 of which shows a cathode ray tube according to the invention, in

part section, Fig. 2 shows the same tube in perspective, and Fig. 3 shows schematically a suitable circuitarrangement for some of the elements of the tube.

Referring now to Fig. 1, a metallic base 1 carries contact pins 2 by which connection with external circuits is made. The pinch 3 supports the various electrodes, the cathode 4 being carried by the supports 5, which are electrically associated with certain of the contact pins 2 by leading-in conductors 1'7. The upper deflecting plates 6 and the lower deflecting plates 7 are mounted on supports 8 which also carry the anode 9. A shield 11 is situated so as to assist in focussing the cathode rays and is carried on support 12,

5 which may be connected to one of the contact pins 2 by a leading-in conductor 18. In order to accurately centre the cathode in the shield, a mica or like insulating disc 13 may be provided. The usual glass bulb l4 and viewing screen 15 are pro- 0 vided.

The cathode 4 is preferably a flat strip filament, bent hairpin shape, to produce two parallel arms joined by a small square portion which is coated with active material. This small square portion thus form a single emissive spot, giving a beam of very small cross section. The cathode may be energized from a battery 30 in series with a variable resistance 31 as shown in Fig. 3.

The anode 9 is provided with an aperture 16 immediately above the active portion of the tery 34. It has been found that this form of anode cathode, by means of which the cathode rays are focussed into an intense and narrow beam. A convenient positive potential for the anode is about 300 volts which may be obtained from a batgives a higher ratio of actual beam current to total anode current than can be obtained With the usual form of tubular anode.

The cathode 4 is surrounded by a shield 11, as was stated above. This arrangement in conjunction with the disc anode forms the electron gun of the tube and produces a very sharp intense spot on the screen. In operation, the shield is preferably connected to a source of positive potential, instead of negative as heretofore, and it is convenient to make this connection through a potentiometer 33 in order that the potential on the shield may be varied for focussing. It is believed that by using a positive poten ial on the shield the potentials of the shield and anode are so arranged relative to the cathode that the lines of force from anode to cathode or vice versa, pass with least divergence through the aperture in the anode. The use of a positive potential on the shield also allows the cathode to be moved back from the anode, with a consequent reduction in the effect of errors of alignment.

The positive potential gives rise to no danger of destruction of the cathode by positive ion bombardment, since in practice the shield is only slightly positive with respect to the cathode and therefore takes all the high voltage ions, which are the only ones likely to damage the cathode.

The deflector plates are arranged in pairs at right angles'symmetrically around the gun hole, in the usual manner. As was described above, the plates 6 and 7 are mounted on supports 8 and 19, respectively which also carry the anode 9. The supports 8 and 19 pass through suitable holes in the anode which is insulated from'certain of the supports, for example by mica discs 20 fitting the anode disc and clamped thereto by a flange on the circumference of the anode disc or by other suitable means. One plate of each pair of plates 6 and '7 is connected to a corresponding one of the contact pins 2 by leading-in conductors 21 and 22, respectively. The other plate of each pair of plates 6 and 7 is connected to the anode 9 by metallic bushings 23 and 24, respectively. One

of the supports 19 may be connected to the shell 1 by a leading-in conductor 25 as shown in Fig. 1.

One of these mica discs (the one nearest the cathode) may have an enlarged central aperture which serves to position the upper'end of the 1 shield 11.

The tube may contain argon or other suitable gas at low pressure in accordance with known practice.

It will be apparent that various modifications may be made to the tube described. For instance,

the connection to the deflecting plates may be taken through the walls of the bulb instead of to the base, and this may be convenient it extremely high insulation resistance is required between the plates.

What is claimed is:

1. A cathode ray discharge device comprising an enclosing vessel having a stem, a cathode, a plurality of supports extending from said stem, deflector plates carried by said supports, and a disc anode mounted on said supports in juxtaposition to and having an aperture in alignment with said cathode.

2. A cathode ray discharge device comprising an enclosing vessel having a stem, a cathode mounted on said stem, a plurality of rods extending from said stem, an insulating member supported by said rods, and a disc anode on said insulating member, said anode and insulating member having aligned apertures in juxtaposition to said cathode.

3. A cathode ray discharge device comprising an enclosing vessel having a stem, a cathode mounted on said stem, a plurality of rods extending from said stem, deflector plates carried by said rods, an apertured insulating disc supported by said rods, a tubular screen encircling said cathode and disposed coaxially with respect to the aperture in said insulating disc, and a disc anode on said insulating disc, said anode having a restricted aperture in alignment with the aperture in said insulating disc.

4. A cathode ray discharge device comprising an enclosing vessel having a stem, a cathode, a plurality 0! supports extending from said stem, and an anode assembly mounted on said supports including a flat insulating member and a flat disc anode disposed in operative relation to said cathode and having its edge clamped about the edge or said insulating member.

5. A cathode ray discharge device comprising an enclosing vessel having a stem, a cathode mounted on said stem, a plurality of rods extending from said stem, an anode assembly mounted on said rods including a flat insulating member, a flat disc anode having its edge clamped about the edge of said insulating member, said insulating member and said disc anode having coaxial apertures in alignment with said cathode, and a cylindrical shield encircling said cathode, said shield being coaxially disposed with respect to the apertures in said anode and insulating memher and fitted at one end in the aperture in said 

